Interaction in unity with Gradient via jobs + burst

.Interaction in unity with Gradient via jobs + burst.cs

Interaction in unity with Gradient via jobs + burst

var gradient = new Gradient();

//Access Gradient.colorKeys and Gradient.alphaKey via NativeArray without a Garbage Collector:

//Single threaded mode:
var gradientPtr = gradient.DirectAccess();
using var colorKeys = gradientPtr->GetColorKeys(Allocator.Temp);
using var alphaKeys = gradientPtr->GetAlphaKeys(Allocator.Temp);
var color = gradientPtr->Evaluate(0.6f);

//Multithreaded mode:
var gradientReadOnly = gradient.DirectAccessReadOnly();
using var colorKeys = gradientReadOnly.GetColorKeys(Allocator.Temp);
using var alphaKeys = gradientReadOnly.GetAlphaKeys(Allocator.Temp);
var color = gradientReadOnly.Evaluate(0.6f);


//Job example:
[BurstCompile(OptimizeFor = OptimizeFor.Performance)]
private unsafe struct GradientBurstJob : IJob
{
    public NativeArray<float4> result;
    [NativeDisableUnsafePtrRestriction] public GradientStruct* gradient;
    
    public void Execute()
    {
        var time = 1f;
        var color = float4.zero;
        
        for (var i = 0; i < 100000; i++)
        {
            time *= 0.9999f;
            color += gradient->Evaluate(time);
        }
        result[0] = color;
    }
}
    
using var nativeArrayResult = new NativeArray<float4>(1, Allocator.TempJob);
var job = new GradientBurstJob
{
    result = nativeArrayResult,
    gradient = gradient.DirectAccess()
};
var jobHandle = job.Schedule();
jobHandle.Complete();

GradientUnsafe.cs

/*The MIT License (MIT)
Copyright 2023 https://github.com/viruseg

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.*/

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using Unity.Collections;
using Unity.Collections.LowLevel.Unsafe;
using Unity.Mathematics;
using UnityEngine;

namespace GradientUnsafe
{
    [StructLayout(LayoutKind.Explicit)]
    public unsafe struct GradientStruct
    {
        private const int COLORS_SIZE = 4 * 4 * 8;
        private const int COLOR_TIMES_SIZE = 2 * 8;
        private const int ALPHA_TIMES_SIZE = 2 * 8;
        private const int COLOR_COUNT_SIZE = 1;
        private const int ALPHA_COUNT_SIZE = 1;
        
        private const int COLORS_OFFSET = 0;
        private const int COLOR_TIMES_OFFSET = COLORS_SIZE;
        private const int ALPHA_TIMES_OFFSET = COLORS_SIZE + COLOR_TIMES_SIZE;
        private const int COLOR_COUNT_OFFSET = COLORS_SIZE + COLOR_TIMES_SIZE + ALPHA_TIMES_SIZE;
        private const int ALPHA_COUNT_OFFSET = COLORS_SIZE + COLOR_TIMES_SIZE + ALPHA_TIMES_SIZE + COLOR_COUNT_SIZE;
        
        [FieldOffset(COLORS_OFFSET)] private fixed byte colors[COLORS_SIZE];
        [FieldOffset(COLOR_TIMES_OFFSET)] private fixed byte colorTimes[COLOR_TIMES_SIZE];
        [FieldOffset(ALPHA_TIMES_OFFSET)] private fixed byte alphaTimes[ALPHA_TIMES_SIZE];
        [FieldOffset(COLOR_COUNT_OFFSET)] private byte colorCount;
        [FieldOffset(ALPHA_COUNT_OFFSET)] private byte alphaCount;

        #if UNITY_2022_2_OR_NEWER
            private const int MODE_SIZE = 1;
            
            private const int MODE_OFFSET = COLORS_SIZE + COLOR_TIMES_SIZE + ALPHA_TIMES_SIZE + COLOR_COUNT_SIZE + ALPHA_COUNT_SIZE;
            private const int COLOR_SPACE_OFFSET = COLORS_SIZE + COLOR_TIMES_SIZE + ALPHA_TIMES_SIZE + COLOR_COUNT_SIZE + ALPHA_COUNT_SIZE + MODE_SIZE;
            
            [FieldOffset(MODE_OFFSET)] private byte mode;
            [FieldOffset(COLOR_SPACE_OFFSET)] private byte colorSpace;
        #else
            private const int DUMMY0_SIZE = 1;
            private const int DUMMY1_SIZE = 1;

            private const int DUMMY0_OFFSET = COLORS_SIZE + COLOR_TIMES_SIZE + ALPHA_TIMES_SIZE + COLOR_COUNT_SIZE + ALPHA_COUNT_SIZE;
            private const int DUMMY1_OFFSET = COLORS_SIZE + COLOR_TIMES_SIZE + ALPHA_TIMES_SIZE + COLOR_COUNT_SIZE + ALPHA_COUNT_SIZE + DUMMY0_SIZE;
            private const int MODE_OFFSET = COLORS_SIZE + COLOR_TIMES_SIZE + ALPHA_TIMES_SIZE + COLOR_COUNT_SIZE + ALPHA_COUNT_SIZE + DUMMY0_SIZE + DUMMY1_SIZE;

            [FieldOffset(DUMMY0_OFFSET)] private byte dummy0;
            [FieldOffset(DUMMY1_OFFSET)] private byte dummy1;
            [FieldOffset(MODE_OFFSET)] private byte mode;
        #endif
        
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private float4* Color(int index)
        {
            fixed(byte* colorsPtr = colors) return (float4*) colorsPtr + index;
        }
        
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private ushort* ColorTime(int index)
        {
            fixed(byte* colorTimesPtr = colorTimes) return (ushort*) colorTimesPtr + index;
        }
        
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private ushort* AlphaTime(int index)
        {
            fixed(byte* alphaTimesPtr = alphaTimes) return (ushort*) alphaTimesPtr + index;
        }
        
        public float4 Color0
        {
            get => *Color(0);
            set => *Color(0) = value;
        }
        public float4 Color1
        {
            get => *Color(1);
            set => *Color(1) = value;
        }
        public float4 Color2
        {
            get => *Color(2);
            set => *Color(2) = value;
        }
        public float4 Color3
        {
            get => *Color(3);
            set => *Color(3) = value;
        }
        public float4 Color4
        {
            get => *Color(4);
            set => *Color(4) = value;
        }
        public float4 Color5
        {
            get => *Color(5);
            set => *Color(5) = value;
        }
        public float4 Color6
        {
            get => *Color(6);
            set => *Color(6) = value;
        }
        public float4 Color7
        {
            get => *Color(7);
            set => *Color(7) = value;
        }
        
        public float ColorTime0
        {
            get => *ColorTime(0) / 65535f;
            set => *ColorTime(0) = (ushort) (65535 * value);
        }
        public float ColorTime1
        {
            get => *ColorTime(1) / 65535f;
            set => *ColorTime(1) = (ushort) (65535 * value);
        }
        public float ColorTime2
        {
            get => *ColorTime(2) / 65535f;
            set => *ColorTime(2) = (ushort) (65535 * value);
        }
        public float ColorTime3
        {
            get => *ColorTime(3) / 65535f;
            set => *ColorTime(3) = (ushort) (65535 * value);
        }
        public float ColorTime4
        {
            get => *ColorTime(4) / 65535f;
            set => *ColorTime(4) = (ushort) (65535 * value);
        }
        public float ColorTime5
        {
            get => *ColorTime(5) / 65535f;
            set => *ColorTime(5) = (ushort) (65535 * value);
        }
        public float ColorTime6
        {
            get => *ColorTime(6) / 65535f;
            set => *ColorTime(6) = (ushort) (65535 * value);
        }
        public float ColorTime7
        {
            get => *ColorTime(7) / 65535f;
            set => *ColorTime(7) = (ushort) (65535 * value);
        }
        
        public float AlphaTime0
        {
            get => *AlphaTime(0) / 65535f;
            set => *AlphaTime(0) = (ushort) (65535 * value);
        }
        public float AlphaTime1
        {
            get => *AlphaTime(1) / 65535f;
            set => *AlphaTime(1) = (ushort) (65535 * value);
        }
        public float AlphaTime2
        {
            get => *AlphaTime(2) / 65535f;
            set => *AlphaTime(2) = (ushort) (65535 * value);
        }
        public float AlphaTime3
        {
            get => *AlphaTime(3) / 65535f;
            set => *AlphaTime(3) = (ushort) (65535 * value);
        }
        public float AlphaTime4
        {
            get => *AlphaTime(4) / 65535f;
            set => *AlphaTime(4) = (ushort) (65535 * value);
        }
        public float AlphaTime5
        {
            get => *AlphaTime(5) / 65535f;
            set => *AlphaTime(5) = (ushort) (65535 * value);
        }
        public float AlphaTime6
        {
            get => *AlphaTime(6) / 65535f;
            set => *AlphaTime(6) = (ushort) (65535 * value);
        }
        public float AlphaTime7
        {
            get => *AlphaTime(7) / 65535f;
            set => *AlphaTime(7) = (ushort) (65535 * value);
        }
        
        public int ColorCount
        {
            get => colorCount;
            set
            {
                #if ENABLE_UNITY_COLLECTIONS_CHECKS
                    if (value < 2 || value > 8) IncorrectCount();
                #endif
                
                colorCount = (byte) value;
            }
        }

        public int AlphaCount
        {
            get => alphaCount;
            set
            {
                #if ENABLE_UNITY_COLLECTIONS_CHECKS
                    if (value < 2 || value > 8) IncorrectCount();
                #endif
                
                alphaCount = (byte) value;
            }
        }
        
        public GradientMode Mode
        {
            get => (GradientMode) mode;
            set => mode = (byte) value;
        }
        
        #if UNITY_2022_2_OR_NEWER
            public ColorSpace ColorSpace
            {
                get => colorSpace == 255 ? ColorSpace.Uninitialized : (ColorSpace) colorSpace;
                set => colorSpace = value == ColorSpace.Uninitialized ? (byte) 255 : (byte) value;
            }
        #endif
        
        public void SetColorKey(int index, GradientColorKeyBurst value)
        {
            #if ENABLE_UNITY_COLLECTIONS_CHECKS
                if (index < 0 || index > 7) IncorrectIndex();
            #endif

            Color(index)->xyz = value.color.xyz;
            *ColorTime(index) = (ushort) (65535 * value.time);
        }

        public GradientColorKeyBurst GetColorKey(int index)
        {
            #if ENABLE_UNITY_COLLECTIONS_CHECKS
                if (index < 0 || index > 7) IncorrectIndex();
            #endif

            return new GradientColorKeyBurst(*Color(index), *ColorTime(index) / 65535f);
        }

        public void SetColorKeys(NativeArray<GradientColorKeyBurst> colorKeys)
        {
            #if ENABLE_UNITY_COLLECTIONS_CHECKS
                if (colorKeys.Length < 2 || colorKeys.Length > 8) IncorrectLength();
            #endif

            var colorKeysTmp = new NativeArray<GradientColorKeyBurst>(colorKeys, Allocator.Temp);
            colorKeysTmp.Sort<GradientColorKeyBurst, GradientColorKeyComparer>(default);

            colorCount = (byte) colorKeys.Length;
            
            for (var i = 0; i < colorCount; i++)
            {
                SetColorKey(i, colorKeysTmp[i]);
            }

            colorKeysTmp.Dispose();
        }

        public void SetColorKeysWithoutSort(NativeArray<GradientColorKeyBurst> colorKeys)
        {
            #if ENABLE_UNITY_COLLECTIONS_CHECKS
                if (colorKeys.Length < 2 || colorKeys.Length > 8) IncorrectLength();
            #endif

            colorCount = (byte) colorKeys.Length;
            
            for (var i = 0; i < colorCount; i++)
            {
                SetColorKey(i, colorKeys[i]);
            }
        }
        
        public NativeArray<GradientColorKeyBurst> GetColorKeys(Allocator allocator)
        {
            var colorKeys = new NativeArray<GradientColorKeyBurst>(colorCount, allocator);
            
            for (var i = 0; i < colorCount; i++)
            {
                colorKeys[i] = GetColorKey(i);
            }

            return colorKeys;
        }
        
        public void SetAlphaKey(int index, GradientAlphaKey value)
        {
            #if ENABLE_UNITY_COLLECTIONS_CHECKS
                if (index < 0 || index > 7) IncorrectIndex();
            #endif

            Color(index)->w = value.alpha;
            *AlphaTime(index) = (ushort) (65535 * value.time);
        }

        public GradientAlphaKey GetAlphaKey(int index)
        {
            #if ENABLE_UNITY_COLLECTIONS_CHECKS
                if (index < 0 || index > 7) IncorrectIndex();
            #endif

            return new GradientAlphaKey(Color(index)->w, *AlphaTime(index) / 65535f);
        }
        
        public void SetAlphaKeys(NativeArray<GradientAlphaKey> alphaKeys)
        {
            #if ENABLE_UNITY_COLLECTIONS_CHECKS
                if (alphaKeys.Length < 2 || alphaKeys.Length > 8) IncorrectLength();
            #endif

            var alphaKeysTmp = new NativeArray<GradientAlphaKey>(alphaKeys, Allocator.Temp);
            alphaKeysTmp.Sort<GradientAlphaKey, GradientAlphaKeyComparer>(default);

            alphaCount = (byte) alphaKeys.Length;
            
            for (var i = 0; i < alphaCount; i++)
            {
                SetAlphaKey(i, alphaKeys[i]);
            }

            alphaKeysTmp.Dispose();
        }
        
        public void SetAlphaKeysWithoutSort(NativeArray<GradientAlphaKey> alphaKeys)
        {
            #if ENABLE_UNITY_COLLECTIONS_CHECKS
                if (alphaKeys.Length < 2 || alphaKeys.Length > 8) IncorrectLength();
            #endif

            alphaCount = (byte) alphaKeys.Length;
            
            for (var i = 0; i < alphaCount; i++)
            {
                SetAlphaKey(i, alphaKeys[i]);
            }
        }

        public NativeArray<GradientAlphaKey> GetAlphaKeys(Allocator allocator)
        {
            var alphaKeys = new NativeArray<GradientAlphaKey>(alphaCount, allocator);
            
            for (var i = 0; i < alphaCount; i++)
            {
                alphaKeys[i] = GetAlphaKey(i);
            }

            return alphaKeys;
        }
        
        private static void IncorrectIndex() => throw new Exception("The index should be between 0 and 7.");
        private static void IncorrectCount() => throw new Exception("The number should be in the range of 2 to 8.");
        private static void IncorrectLength() => throw new Exception("The length of the array must be in the range of 2 to 8.");
        
        public float4 Evaluate(float time)
        {
            float3 color = default;
            var colorCalculated = false;

            var colorKey = GetColorKey(0);
            if (time <= colorKey.time)
            {
                color = colorKey.color.xyz;
                colorCalculated = true;
            }
            
            if (!colorCalculated)
                for (var i = 0; i < colorCount - 1; i++)
                {
                    var colorKeyNext = GetColorKey(i + 1);
                        
                    if (time <= colorKeyNext.time)
                    {
                        if (Mode == GradientMode.Blend)
                        {
                            var localTime = (time - colorKey.time) / (colorKeyNext.time - colorKey.time);
                            color = math.lerp(colorKey.color.xyz, colorKeyNext.color.xyz, localTime);
                        }
                        #if UNITY_2022_2_OR_NEWER
                            else if (Mode == GradientMode.PerceptualBlend)
                            {
                                var localTime = (time - colorKey.time) / (colorKeyNext.time - colorKey.time);
                                color = OklabToLinear(math.lerp(LinearToOklab(colorKey.color.xyz), LinearToOklab(colorKeyNext.color.xyz), localTime));
                            }
                        #endif
                        else
                        {
                            color = colorKeyNext.color.xyz;
                        }
                        colorCalculated = true;
                        break;
                    }
                    
                    colorKey = colorKeyNext;
                }

            if (!colorCalculated) color = colorKey.color.xyz;
            
            
            
            float alpha = default;
            var alphaCalculated = false;
            
            var alphaKey = GetAlphaKey(0);
            if (time <= alphaKey.time)
            {
                alpha = alphaKey.alpha;
                alphaCalculated = true;
            }
            
            if (!alphaCalculated)
                for (var i = 0; i < alphaCount - 1; i++)
                {
                    var alphaKeyNext = GetAlphaKey(i + 1);
                        
                    if (time <= alphaKeyNext.time)
                    {
                        if (Mode == GradientMode.Blend
                                #if UNITY_2022_2_OR_NEWER
                                    || Mode == GradientMode.PerceptualBlend
                                #endif
                            )
                        {
                            var localTime = (time - alphaKey.time) / (alphaKeyNext.time - alphaKey.time);
                            alpha = math.lerp(alphaKey.alpha, alphaKeyNext.alpha, localTime);
                        }
                        else
                        {
                            alpha = alphaKeyNext.alpha;
                        }
                        alphaCalculated = true;
                        break;
                    }
                    
                    alphaKey = alphaKeyNext;
                }
            
            if (!alphaCalculated) alpha = alphaKey.alpha;
                
            return new float4(color, alpha);
        }
        
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static float3 CubeRoot(float3 val)
        {
            return math.pow(math.abs(val), 1f / 3f) * math.sign(val);
        }
        
        #if UNITY_2022_2_OR_NEWER
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            private static float3 LinearToGammaSpace(float3 linRGB)
            {
                linRGB = math.max(linRGB, float3.zero);
                return math.max(1.055f * math.pow(linRGB, 0.416666667f) - 0.055f, 0);
            }
            
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            private static float3 GammaToLinearSpace(float3 sRGB)
            {
                return sRGB * (sRGB * (sRGB * 0.305306011f + 0.682171111f) + 0.012522878f);
            }
            
            private float3 LinearToOklab(float3 c)
            {
                if (ColorSpace != ColorSpace.Linear) c = GammaToLinearSpace(c);

                var result = new float3(
                    math.dot(c, new float3(0.4122214708f, 0.5363325363f, 0.0514459929f)),
                    math.dot(c, new float3(0.2119034982f, 0.6806995451f, 0.1073969566f)),
                    math.dot(c, new float3(0.0883024619f, 0.2817188376f, 0.6299787005f)));

                result = CubeRoot(result);
                
                return new float3(
                    math.csum(new float3(0.2104542553f, 0.7936177850f, -0.0040720468f) * result.xyz),
                    math.csum(new float3(1.9779984951f, -2.4285922050f, 0.4505937099f) * result.xyz),
                    math.csum(new float3(0.0259040371f, 0.7827717662f, -0.8086757660f) * result.xyz)
                );
            }

            private float3 OklabToLinear(float3 c) 
            {
                var result = new float3(
                    math.csum(new float3(1,  0.3963377774f,  0.2158037573f) * c.xyz),
                    math.csum(new float3(1, -0.1055613458f, -0.0638541728f) * c.xyz),
                    math.csum(new float3(1, -0.0894841775f, -1.2914855480f) * c.xyz)
                );

                result = result * result * result;
                
                result = new float3(
                    math.csum(new float3( 4.0767416621f, -3.3077115913f,  0.2309699292f) * result.xyz),
                    math.csum(new float3(-1.2684380046f,  2.6097574011f, -0.3413193965f) * result.xyz),
                    math.csum(new float3(-0.0041960863f, -0.7034186147f,  1.7076147010f) * result.xyz)
                );
                
                if (ColorSpace != ColorSpace.Linear) result = LinearToGammaSpace(result);

                return result;
            }
        #endif

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static ReadOnly AsReadOnly(GradientStruct* data) => new ReadOnly(data);
        
        public readonly struct ReadOnly
        {
            [NativeDisableUnsafePtrRestriction] private readonly GradientStruct* ptr;

            public ReadOnly(GradientStruct* ptr)
            {
                this.ptr = ptr;
            }
            
            public int ColorCount => ptr->ColorCount;
            
            public int AlphaCount => ptr->AlphaCount;
            
            public GradientMode Mode => ptr->Mode;
            
            #if UNITY_2022_2_OR_NEWER
                public ColorSpace ColorSpace => ptr->ColorSpace;
            #endif
            
            public GradientColorKeyBurst GetColorKey(int index) => ptr->GetColorKey(index);
            
            public NativeArray<GradientColorKeyBurst> GetColorKeys(Allocator allocator) => ptr->GetColorKeys(allocator);
            
            public GradientAlphaKey GetAlphaKey(int index) => ptr->GetAlphaKey(index);
            
            public NativeArray<GradientAlphaKey> GetAlphaKeys(Allocator allocator) => ptr->GetAlphaKeys(allocator);
            
            public float4 Evaluate(float time) => ptr->Evaluate(time);
        }
        
        private struct GradientColorKeyComparer : IComparer<GradientColorKeyBurst>
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public int Compare(GradientColorKeyBurst v1, GradientColorKeyBurst v2)
            {
                return v1.time.CompareTo(v2.time);
            }
        }
        
        private struct GradientAlphaKeyComparer : IComparer<GradientAlphaKey>
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public int Compare(GradientAlphaKey v1, GradientAlphaKey v2)
            {
                return v1.time.CompareTo(v2.time);
            }
        }
    }
    
    internal readonly struct GradientColorKeyBurst
    {
        public readonly float4 color;
        public readonly float time;

        public GradientColorKeyBurst(float4 color, float time)
        {
            this.color = color;
            this.time = time;
        }
    }

    internal static class GradientExt
    {
        private static readonly int m_PtrOffset;
        
        static GradientExt()
        {
            var m_PtrMember = typeof(Gradient).GetField("m_Ptr", BindingFlags.Instance | BindingFlags.NonPublic);

            m_PtrOffset = UnsafeUtility.GetFieldOffset(m_PtrMember);
        }
        
        private static unsafe IntPtr Ptr(this Gradient gradient)
        {
            var ptr = (byte*) UnsafeUtility.PinGCObjectAndGetAddress(gradient, out var handle);
            var gradientPtr = *(IntPtr*) (ptr + m_PtrOffset);
            UnsafeUtility.ReleaseGCObject(handle);

            return gradientPtr;
        }

        /// <summary>
        /// Assigns a value to the original class from the copy.
        /// </summary>
        public static unsafe void SetData(this Gradient gradient, GradientStruct value)
        {
            *(GradientStruct*) gradient.Ptr() = value;
        }
        
        /// <summary>
        /// A copy of the gradient not bound to the original class.
        /// </summary>
        public static unsafe GradientStruct GetData(this Gradient gradient)
        {
            var ptr = gradient.Ptr();
            GradientStruct result = default;
            UnsafeUtility.MemCpy(&result, (void*) ptr, sizeof(GradientStruct));
            return result;
        }
        
        /// <summary>
        /// Direct access to the original class memory.
        /// </summary>
        public static unsafe GradientStruct* DirectAccess(this Gradient gradient)
        {
            return (GradientStruct*) gradient.Ptr();
        }
        
        /// <summary>
        /// Direct access to the memory of the original class. Read only. Suitable for multithreading.
        /// </summary>
        public static unsafe GradientStruct.ReadOnly DirectAccessReadOnly(this Gradient gradient)
        {
            return GradientStruct.AsReadOnly(gradient.DirectAccess());
        }
    }
}

Hello, thank you very much for your contribution, it works perfectly !
What is the license of your code ? Could I use it in any project, commercial or not ? Thanks !

@felixcantet
Added a license. You can do whatever you want with this code.